1. Field of the Invention
This invention relates to a novel N-alkylaspartyl dipeptide ester compounds, a sweetening agent or a sweetened food or similar products comprising the compound as an effective component. The invention further provides methods of imparting sweetness in a product and methods of making the N-alkylaspartyl dipeptide ester compounds.
2. Discussion of the Background
In recent years, as eating habits and products eaten have changed, fatness caused by excessive sugar intake and diseases caused by fatness have been of significant concern. Accordingly, the development of a low-calory sweetener (sweetening agent) that replaces sugar has been in demand. A sweetener that has been widely used is aspartame which is excellent in safety, quality of sweetness and taste properties. However, there are problems with aspartame with respect to its stability. WO 94/11391 states that compounds in which an alkyl group is introduced on a nitrogen atom of aspartic acid in the aspartame markedly improves the sweetening potency and also results in a slight improvement in the stability of the compound. The best compound described in WO 94/11391 is N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester having a 3,3-dimethylbutyl group as an alkyl group and which has a sweetening potency of 10,000 times that of sucrose (the value is obtained by comparing the compound to 2%, 5% and 10% sucrose solutions).
Aspartame compounds having 20 different substituents other than the 3,3-dimethylbutyl group are also disclosed where the compounds have sweetening potencies less than 2,500 times that of sucrose. Compounds having a 3-(substituted phenyl) propyl group as an alkyl group are also shown. Among these, N-[N-(3-phenylpropyl)-L-(α-aspartyl]-L-phenylalanine 1-methyl ester and N-[N-(3-(3-methoxy-4-hydroxyphenylpropyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester are described as having sweetening potencies of 1500 and 2500 times that of sucrose, respectively. These sweetening potencies are far less than that of N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester, which is 10,000 times that of sucrose. Further described are N-[N-[(RS)-3-phenylbutyl]-L-(α-aspartyl]-L-phenylalanine 1-methylester, which has as an alkyl group a 3-phenyl propyl group to the third position of which a methyl group is introduced, that is a 3-phenyl butyl group, is reported to have a sweetening potency of 1,200 times that of sucrose. The N-[N-(3-phenylpropyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester has a lower sweetening potency due to the methyl group introduced at the third position.
Furthermore, N-[N-[3-(3-methoxy-4-hydroxyphenyl)(RS)-1-methylpropyl]-L-α-aspartyl]-L-phenylalanine 1-methylester, having a structure corresponding to N-[N[3-(3-methoxy-4-hydroxyphenyl) propyl)-L-(α-aspartyl]-L-phenylalanine 1-methyl ester, with a methyl group on the first position of the propyl group is reported to have a sweetening potency of 500 times that of sucrose. The significantly lower sweetening potency is due to the methyl group on the the propyl group.
Another example of replacing the L-phenylalanine methyl ester moiety with another amino acid ester is N-[N-(3,3-dimethylbutyl)-L-α-aspartyl]-L-tyrosine 1-methyl ester which has a sweetening potency of 4,000 times that of sucrose.
In view of the foregoing, development of a low-calory sweetener having a superior sweetening potency is in demand.
Thus, the present inventors sought to solve the long-standing problems associated with prior low-calory sweeteners and provide novel N-alkylaspartyl dipeptide ester compounds which are excellent in safety and which have sweetening potencies equal to or higher than that of N-[N-(3,3-dimethylbutyl]-L-α-aspartyl]-L phenylalanine 1-methylester, and a low-calory sweetening agent comprising the compound as an effective component.